The use of Personal Area Networking (PAN) and RFID wireless interfaces is growing. Cell phones may act as an RFID reader/client in many applications such as electronic transactions, inventory, or medical monitoring, among others. These additional wireless interfaces may allow the phone's processor to communicate with the alternative hardware/software platforms other than the mobile phone platform.
Micro-SD cards, Mini-PCI, or other formats may be used to accomplish the PAN or RFID communication, however building the adjunct wireless-enabling circuits into a cell phone or other electronic device may be too expensive, and/or may reduce the phone user's ability to use a plug-in card for other applications.
Many PAN and RFID interfaces are engineered to the point of becoming chip radios: the entire stack is contained in a single, low-cost, low-power integrated circuit.